The present invention relates to a mounting structure of a water pump for an engine, and more particularly to a water pump used in the engine for a vehicle such as a snowmobile.
A conventional water pump is provided on the engine for circulating a coolant in a cooling system. Generally, the pump is driven by a driven pulley and a belt from a drive pulley mounted on a crankshaft of the engine.
FIG. 2 shows a mounting structure of the conventional water pump.
A magneto rotor 3 is securely mounted on a crankshaft 1 of an engine by a nut 2. An output member 6 of a recoil starter 5 is connected to the magneto rotor 3 with bolts 10 interposing a drive pulley 4 there-between. A water pump 12 is secured to a cylinder block 11 of the engine. The water pump 12 has an impeller shaft 13 on which an impeller 18 is securely mounted. A driven pulley 15 of the water pump 12 is fixed on the impeller shaft 13 at the other end projected from the water pump 12. A V-belt 16 is provided between the pulleys 4 and 15. A safety cover 19 is secured to the cylinder block 11 to cover the driven pulley 15 and the belt 16.
When the crankshaft 1 rotates, rotating power is transmitted to the impeller shaft 13 through the drive pulley 4, the belt 16, and the pulley 15, so that the impeller 18 mounted on the impeller shaft 13 is rotated to feed the coolant in the cooling system.
In the structure, large tension of the belt 16 is exerted on the crankshaft 1 and the impeller shaft 13. Since the shafts 1 and 13 are cantilevered, the crankshaft 1 must have an unnecessary large diameter to bear the large tension. Furthermore, the cover 19 causes the size and weight of the engine to increase.
In order to solve these problems, the water pump 12 may be coaxially provided with the crankshaft 1. However, since the recoil starter 5 is also mounted on the crankshaft 1, the crankshaft 1 must be long. As a result, center of gravity of the crankshaft 1 comes to the side of the recoil starter 5, so that vibration of the crankshaft 1 may occur.